The present invention relates to a method, and a device for operating a microphone system; particularly in a motor vehicle.
Microphones and microphone systems are especially needed in motor vehicles for operating the so-called handsfree telephone. However, they are also needed in voice amplification and communication systems, and in systems for actively suppressing noise.
In this regard, it is important that the sound is, or can be picked up in direct proximity to the head of the vehicle occupant or the vehicle driver. To this end, microphones are generally disposed in the area of the dashboard, in the area of the roof panel, or on the interior mirror. Simple microphones or microphone systems often present a problem for otherwise simple intercoms in car phones, or also for voice-controlled input interfaces on electronic devices. In this case, the voice messages are superposed by driving noises, which is not only problematic with handsfree telephones, but also with voice-controlled input units.
A voice-operated control device for components in motor vehicles is described in, for example, German Unexamined Patent Application No. 196 08 869, where the operation of the control device by means of speech generates a check-back signal, through which it can be determined whether the control device has correctly received the voice-controlled command. Even with regard to its microphone arrangement, a voice-operated control device of this type is only based on a conventional microphone design or microphone arrangement.
A similar type of voice-controlled operating control method is described in German Patent No. 195 33 541. However, the voice-control is treated as such here. In order to achieve secure control, a very expensive voice recognition method is used in which the aspects of noise reduction, echo compensation, feature extraction, and syntax and semantics testing are processed separately from each other. In this case, the aim is simply to postprocess the available voice signals in the best possible manner. An improvement of the voice quality as such, i. e. an improvement of the voice-signal reception, is not considered here.
EP 0721178 A 2 describes a multichannel communication system having a plurality of microphones and a plurality of loudspeakers. In this case, the entire system is designed for at least two people speaking, who are connected to each other in transmit/receive mode. The transmitting means select the voice message from an entire noise background. In a motor-vehicle application, a so-called error or comparison microphone is brought very close to the person speaking, by the seat belt. The location of the microphone is fixed here. Furthermore, the design in this document is for transmit/receive mode for two or more persons.
Along these lines, a frequency-selective control system for acoustic systems is known from EP 0773531 A 2. In this case, the prevention of oversteering is in the forefront. Improving the reception quality of the voice message is not a consideration here. A similar type of system is also known from EP 0721179 A 2. The main objective of the adaptive, tonal control system described therein for eliminating stability problems is to prevent the above-mentioned oversteering, as well.
U.S. Pat. No. 5,539,859 describes a method for reducing noise, which relates exclusively to two microphones acting permanently in reciprocity to each other. A spatial determination specially for obtaining a virtual microphone location is not conducted.
EP 0472356 A1 describes a device, where only the location of the speech or command source is determined by microphones.
This cross-section of the related art indicates that one is principally concerned with improving the already received voice signal. However, improving the reception quality at the location where the speech is generated is frequently, if not fundamentally, neglected.
Therefore, the present invention is based on the object of further developing a method and a device of the species, to the effect that the reception quality of the voice signal input into the system is fundamentally improved.
The stated object of the present invention is achieved by a method of the species, using the characterizing features of Claim 1.
With regard to a device of the species, the stated object of the present invention is achieved by the characterizing features of Claim 4.
Additional advantageous refinements of the method according to the invention are specified in claims 2 through 3, and ongoing refinements regarding the device of the present invention are mentioned in the remaining claims 5 through 8.
The central idea of the present invention, in regard to both the method and the device, is to establish a virtual, optimized microphone location. Normally, this is virtually defined there as the location of the speech source, i.e. the location of the head of the person who is speaking. This so-called spatial noise- or speech-source recognition can be accomplished, e.g. using propagation-delay measurement. In a system of multiple microphones, propagation-delay measurement enables the spatial position of the speech source to be detected while one is speaking. The microphones are added up according to magnitude and phase, in such a manner, that the useful signals are added up and amplified, but the interference signals not correlated to the useful signal are optimally blanked out. Consequently, all of the microphones have a supporting function, and are included in the evaluation. This is not a question of post-processing the microphone signal, but rather improving the speech signal fed into the transmission chain.
The root idea of both the method and device according to the present invention is especially advantageous, because a microphone selected in this manner, or the propagation-delay measurement forming the basis of this, can be combined with a head-position determination of the person speaking.
Means for ascertaining the position of the head, which are used for controlling the air bag, are indeed known from U.S. Pat. No. 5,366,241. However, the head position is detected here using generated sound waves. A combination of this with a voice-operated microphone is not mentioned.
In an additional advantageous refinement, the data on the head position can then be generated via the speech-source recognition or the so-called virtual microphone-location determination, these data being qualified and usable for controlling the safety systems. That is, the head position is also determined here simultaneously to the normal speaking with car phones or speech-input devices, without having to provide additional, more extensive means. So if the head is in an unfavorable position relative to the air bag system, the safety system can be controlled in an emergency, to prevent the air bag from being deployed.
Therefore, the system is multifunctional as a whole. However, it is important that the speech quality is increased at the detection location. This leads to a clearer transmission while talking on the car phone. Furthermore, the voice commands for units in the motor vehicle controlled by voice input are more easily recognized and carried out.